The preferred embodiments relate to ultrasonic transducers and more particularly to a system and method using selective interleaved excitation pulse frequency for such transducers.
Ultrasound transducers are known in the art for transmitting ultrasound waves and detecting a reflection or echo of the transmitted wave. Such devices are also sometimes referred to as ultrasound or ultrasonic transducers or transceivers. Ultrasound transducers have myriad uses, including as water and gas flow meters, consumer devices, vehicle safety, and medical diagnostics. In these and other fields, signals detected by the transducer may be processed to determine distance, which may be further combined with directional or area processing to determine flow, volume, shape, as well as aspects in connection with two and three dimensional processing, including image processing.
Flow meters (e.g., water or gas) are implemented in various schemes in the prior art, including mechanical, electromagnetic, and ultrasonics. Various degrees of human involvement, design considerations, reliability issues, and the like are often involved in the various approaches. With respect to ultrasonic flow meters, the prior art includes a system that includes a two ultrasonic transducers oriented to communicate signals between one another, with the signal traversing a channel inside a pipe. The velocity, or time of flight (TOF), of the water/gas may thus be determined based in part on a difference of the downstream ultrasonic communication and the upstream ultrasonic communication.
While the above and related approaches have served various needs in the prior art, they also provide various drawbacks. Costs associated with human intervention, such as periodic maintenance, upkeep, and calibration are considerations. Power consumption in electronic equipment also may be an issue, either with the related cost of human intervention to change batteries or, even without human intervention, in the lifespan of the battery given the power consumption of the device(s). Moreover, in an ultrasonic flow meter system, issues arise with the excitation frequency of the communication between transducers. For example, in one approach, a phase-locked loop (PLL) may be used to clock each transducer for its transmitted pulses, but such an approach may be costly to implement and typically a PLL may have an undesirably high power consumption. As another example, in systems without a PLL, often a less-expensive and/or lower power-consuming crystal oscillator is used as a clock source, but relative to a PLL, such a system typically has a coarse set of frequency choices, as it is limited to an integer divisor of the nominal clock frequency. In the case where only integer divisions of this frequency are available, then the available frequencies available to use for exciting a transducer may be somewhat limited, particularly given the desired optimization of the transducers. Consider as example such a system with nominal frequency of 8 MHz. With integer divisors of that frequency, there is a relatively small number of different available frequencies available from which to select a frequency to drive the transducers (e.g., 8 MHz/1=8 MHz; 8 MHz/2=4 MHz; 8 MHz/3=2.67 MHz; 8 MHz/4=2 MHz; . . . ; 8 MHz/9=0.89 MHz; 8 MHz/7=1.143. MHz, and so forth). More specifically, it is known in the art that the receiving side of a transducer has an optimum response when excited by its resonant frequency. Thus, for optimum performance, the transmitting side of a transducer should output that resonant frequency. In the above-noted system with an integer divided clock signal, however, the limited frequencies available for exciting the transducer may not match or be sufficiently close to the desirable resonant frequency.
Given the preceding, the present inventors seek to improve upon the prior art, as further detailed below.